Field of the Invention
The present invention relates to an image processing apparatus for performing facsimile communication using deemed voice, a control method thereof, and a storage medium.
Description of the Related Art
Recently, facsimile (FAX) transmission over IP networks, which are high-speed network, is becoming widely used. There are two methods in FAX transmission over an IP network. One of the methods is a transmission standard called ITU-T recommendation T.38 in which signals that are transmitted using the T.30 protocol are transmitted as digital signals without conversion, this method allowing the transmission to be performed at higher speed than T.30. The other is a transmission method using deemed voice, using the ITU-T recommendation T.30 protocol. This is a method in which data digitally modulated into analog signals by a modem and further voice-packetized by a voice codec (CODEC) is transmitted, and is called deemed voice transmission (Inband signaling) because the transmission is performed deeming T.30 analog signals to be voice signals.
In deemed voice transmission having the above-described configuration, it is necessary to modulate digital signals of transmission data into analog signals and further to voice-packetize the obtained signals using voice codec. Alternatively, it is necessary to decode voice packets of received data using voice codec and further to demodulate the obtained signals into digital signals, and, thus, a digital modem with built-in voice codec has been devised that can perform digital input and output. Examples of the voice packet encoding method include ITU-T recommendation G.711 and the like, the RTP (real time protocol) is used as the transmission protocol, and connection to a bus is established via a PCM I/F or the like.
These two methods use the SIP (session initiation protocol), and point-to-point transmission over an IP network is realized. Examples of the IP network include a digital public network called NGN (Next Generation Network) provided by NTT, a private IP line using an IP private branch exchanger (IP-PBX), and the like. In particular, in the case of the NGN, bandwidth guarantee, security management, and the like are performed, and, thus, high-speed and secure image transmission can be realized. In the NGN, 1 Mbps at a maximum is guaranteed, which realizes transmission that is about 30 times faster than a conventional public switched telephone network (PSTN).
Furthermore, an IP telephone is known that realizes a call by packetizing and encoding voice and transmitting and receiving it over an IP network. Using this technique, a call can be realized using a handset and a slave telephone (hereinafter, they may be collectively referred to as a “handset”) of a fax machine. In order to connect a handset to an IP network, an SLIC (subscriber line interface circuit: also referred to as a “subscriber line connection circuit”) for connecting the telephone to the IP network is used. An SLIC is used typically for encoding analog voice into voice packets, detecting hooking of a telephone, identifying dialing signals and the like from a telephone, ringing control of a telephone, or the like. An input and output I/F of an SLIC is for digitalized voice signals as in the case of a digital modem, examples of the voice signal encoding method include ITU-T recommendation G.711 and the like, the RTP (real time protocol) is used as the transmission protocol, and connection to a bus is established via a PCM I/F or the like.
A handset of a fax machine is often used for manual transmission after a call, and, thus, manual transmission has to be supported also in the above-described deemed voice transmission. The manual transmission mode is a mode in which, at the time of transmission, the other party's phone number is input using a connected handset or slave telephone, and, after conversation with the other party, a fax document is immediately transmitted without hanging up the telephone. This mode is advantageous in that wrong transmission can be prevented because a fax document can be transmitted after conversation with the other party. As described above, when realizing manual transmission in the deemed voice transmission, it is necessary to selectively use an SLIC for a call using a handset, and a digital modem for FAX communication. That is to say, it is necessary to select whether a PCM I/F is to be connected to an SLIC or to a digital modem.
Furthermore, in order to establish connection simultaneously to a plurality of connection destinations in a PSTN, it is necessary to connect modular cables in the same number as the number of lines, but, in the case of deemed voice transmission using an IP line, connection of one network cable is sufficient to establish connection simultaneously to a plurality of connection destinations and realize communication and calls. In Such a multi-session environment, for example, in SIP, one connection session is from INVITE to BYE. A first connection is session 1, and its next connection is session 2, that is, the connection is not associated with a physical line.
Japanese Patent No. 3772828 discloses the configuration that switches the connection destination between an SLIC and a digital modem, using a switch. Specifically, this is a technique in which, using a switch, an incoming call to a fixed-line telephone is connected to a fixed-line telephone and an incoming call to an IP telephone is connected via a VoIP gateway to a fixed-line telephone, wherein connection is established to a digital modem if the transmission source is a fax machine, and is established to an SLIC if the transmission source is not a fax machine. However, no description is made of FAX communication using deemed voice realizing the functions such as manual transmission, or of control of a plurality of digital modems.
The above-described conventional technique has a following problem. A fax machine supporting multi-sessions includes digital modems in the same number as the number of sessions necessary for FAX and communication connected simultaneously with the FAX. For example, a fax machine capable of performing simultaneous communication in two sessions includes two digital modems. However, the number of people who can simultaneously use a handset or a slave telephone is one, and the number of handsets or slave telephones connected to the fax machine is typically one. Accordingly, the fax machine includes only one SLIC for controlling the telephone functions. Thus, when performing multi-sessions including deemed voice transmission over an IP network, two digital modems have to exclusively use one SLIC. That is to say, when performing manual transmission, an SLIC is used in a call, and a digital modem is used in subsequent FAX transmission. Thus, it is required that both of the two digital modems be capable of being combined with the SLIC for realizing manual transmission.